Speed responsive means



May 8, 1934. SEELEY I 1,958,250

SPEED RESPONS IVE MEANS Filed June 1, 1931 4t Fi g .2.

7 0 lIUU1Pu 9 i Inventor":

/(, Harold T SeeIe'j,

His Attorney.

P atented May 8 1934 I UNITED STATES PATENT OFFICE SPEED RESPONSIVEMEANS Harold T. Seeley, Lansdowne, Pa., assignor to General ElectricCompany, a corporation of New York Application June 1, 1931, Serial No.541,315 'ZClaims. (01. 171-418) v My invention relates to speedresponsive means the resistor 7 so that the rectifier does not andparticularly to arrangements for effecting a rectify all of the inducedcurrent flowing in the desired operation in response to a predeterminedfield winding 4. The relay 9 may be of any suitsub-synchronous speed ofan alternating current able type, examples of which are well-known inmotor and its object is to provide an improved the ,art, which closesits contacts immediately so arrangement for accomplishing such a result.after the relay winding is energized and which In accordance with myinvention, I provide an opens its contacts after a time delay when theimproved arrangement in the secondary circuit relay winding isdeenergized. Preferably, howv of \an alternating current motor foroperating ever, the relay is of the type having a copper jack- 10 whenthe frequency of the induced current thereeted winding. In order toreduce the impedance 65 in is below a predetermined value. In accordofthe relay circuit so that the relay may receive ance with a preferredembodiment of my invensufiicient induced current to open its contactsim- 1 tion, I accomplish the'desired result by connectmediately afterswitch 3 is closed, it may be deing a half-wave rectifier and thewinding ot a sirable to have a condenser ll'connected across time relayin series in the secondary circuit. the winding of the relay. 70Preferably, the relay is of the well-known slow- To prevent the fieldswitch. 6 from being closed acting type which has a copper jacketedwinding when the switch 3 is open, the circuit "of the closso that itopens its contacts with a time delay ing coil 8 oi the field switch 6also includes the when the relay is deenergized. contacts 13 of a timerelay 14 which is arranged My invention will be better understood fromto be energized to close its-contacts 13 after the75 the followingdescription when taken in connecswitch 3 has been closed a predeterminedtime. tion with the accompanying drawing and its scope As shown in thedrawing, this result is accomwill be pointed out in the appended claims.7 plished by providing the circuit of the winding In the accompanyingdrawing Fig. 1 diagramof the relay 14 with contacts 15 which arearmatically illustrates a synchronous motor startranged to be closed bythe switch 3 when in its 80 ing system embodying my invention, and Fig.2 closed position. I illustrates a modification thereof. The operationof the arrangement shown in Referring to Fig. 1 of the accompanyingdraw- Fig. 1 of the drawifig is as follows: When the ing, 1 represents asynchronous motor which is motor is at rest and the switch 3 is closed,a

arranged to be connected to a suitable supply current of linefrequencyis induced in the field circuit 2 bymeans of a switch 3 whichmay be of winding 4 and this flows through the discharge any suitabletype, examples of which are wellresistor '7. A portion of this currentis rectified known in the art. While I have shown a manuby the rectifier10 and flows through the windally controlled switch, it is obvious tothose skilled ing of the relay 9 so that it'immediately-opens '35 in theart that any suitable automatic means its contacts 16. A predeterminedtime after the '90 may be employ Controlling the p g and switch 3 isclosed, the relay.14 closes its contacts closing thereof. The motor 1 isprovided with 13 but in the meantime the relay 9 is operated to a fieldW d 4 which s a d o be conopen its contacts 16 so that the circuit ofthe closnected to a suitable source of excitation 5 by ing coil 8 is notcompleted. As the speed of the 40 means of a switch 6 which is arrangedto be closed motor increases after the switch 3 is closed, the wh n themot speed increases a v a pr d frequency of the current induced in thefield termined value- The Switch When p is winding 4 decreases, whilethe magnitude of the ra ed o conn a suitable discharge es stor 7 currentmay remain substantially constant until across .the termi the field W ig substantially synchronous speed is reached. 45 In Order to 01056 theSwitch 6 automatically Therefore, as the speed of the motor increases,

wh n the motor p d iHCIGaSBSabOVB a Dredeterthe intervals of zerocurrent in the winding. of mine Value, the swi h 6 is provided With a610$- the relay 9 increase but the copper jacket prevents ing coil 8 thecircuit of which is controlled; in" the relay from closing its contacts16. accordance w th my invention, y means of a As soon as the motorreaches a predetermined 60 relay 9, the winding of which is soconnectedin subsynchronous speed, the intervals of the zero series witha half-wave rectifier 10 that both deurrent become of such long durationthat the vices are connectedin series relation with the field copperjacket is unable to hold the relay in its winding 4 when the switch 61sopen. Preferably energized position. The relay then operates to thewindings of the relay 9 and the rectifier 10 close its contacts 16 andthereby completes the 86 are connected in series across a portion or allof circuit of the closing coil 8 of the field switch 6 110,

across the source of excitation 5. The field switch 6 then closes toconnect the field winding 4 across the source of excitation 5 anddisconnects the discharge resistor '7 and the relay 9 from in-seriesrelation with the field winding 4.

It will be noted that by-choo'sing the polarity of the rectifier 10correctly, the arrangement may be made to apply the excitation to themotor field winding 1 during the most favorable halfcycle of slip. Byusingsuch an arrangement, there is no slipping of a' pole when the motorpulls into synchronism.

In'the modification of my invention illustrated in Fig. 2 I have showntherectifier 10 and the operating winding of the relay 9 in series withthe discharge resistor 7 instead of across a portion thereof.Preferably, there is connected around. the rectifier 10 and'the relay 9another rectifier which is arranged to rectify the half wave of theinduced current which is not rectified by the rectifier 10. Theoperation of this modification is similar to the arrangement illustratedin Fig. 1.

While I have, in accordance with the patentstatutes, shown anddescribedv my invention as applied to a particular system and asembodying various 'devices diagrammatically indicated,

modifications as fall within the true spirit and.

scope of my invention;

What.I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, an electric circuit, a source of variablefrequencyvoltage, means for producing in said circuit uni-directionalcurrent impulses at intervals which vary in accordance with thefrequency of said voltage, a control device, and means energized by saidcurrent impulses for efiecting the operation of said control device whenthe interval between any two successive impulses produced said circuitby said first'mentioned means exceeds a predetermined value. I

2. In combination, an electric circuit, a source ingin said circuituni-directional current impulses at intervals which varyin accordancewith the frequency of said voltage, a control device, and meansresponsive to a predetermined duration of the interval between twosuccessive impulses producedin said circuit by said first mentionedmeans for efiecting the operation of said control device.

'3. In combination, an'alternating current cir-' cuit, an alternatingcurrent machine having a I primary winding and a secondary winding,means for connecting the primary winding to said circuit, rectifyingmeans connected to said secondary winding and arranged to allow inducedcurrent to flow through it during only a portion of each cycle of thevoltage'inducedin said secondary winding when said motor is operating ata sub-- synchronous speed, a control device, and means responsive to theduration of the portion of the cycle of induced voltage during which noinneeaaso I .duced current flows through said rectifying means foreffecting'the operation of said control device when the duration of saidportion of the induced voltage cycle exceeds a predetermined value. c

4. In combination, an alternating current cir- I cuit, an alternatingcurrent machine having a 5 primary winding and a secondary winding,means for connecting the primary winding to said circuit, rectifyingmeans connected to said secondary winding and arranged to allow inducedcurrent to fiow through it during only a portion of each cycle of thevoltage induced in said sec-- means exceeds a predetermined valueincluding a time relay having a winding energized by the rectifiedinduced current.

5. In combination, v an alternating current source, a synchronous motorhaving an armature winding and a field winding, means for connectingsaid armature winding to said source, a control device, a half-waverectifier connected in series relation with said field winding, andmeans for efiecting the operation of said control device when theduration of the portion of each cycle 'of'the induced voltage duringwhich no current flows through said rectifier exceeds a predeter- -minedvalue including a time relay having-a winding connected in seriesrelation with said, rectifier and field winding.

source, a synchronous motor having an armature winding and a fieldwindin means for connecting said armature winding to said source, acontrol device, a resistor connected in series relation with said fieldwinding, a half-wave rectifier connected across a portionof saidresistor, and means for effectingv the operation of said control devicewhen the duration of the half cycle of induced voltage during which noinduced current fiows of variable frequency voltage, means or produ -ithrough said rectifier exceeds a predetermined value including a timerelay having a winding connected in series relation with'said rectifieracross said portion of said resistor.

7. In combination, an alternating current source, a synchronous motorhaving an armature winding and a field winding, means for connectingsaid armature, winding to said source, a control device, a resistorconnected in series relation with saidfield winding, a half-waverectifier con-v 6. In combination, an alternating current nected acrossa portion of said resistor, and means across said portion of saidresistor, and a con denser connected in shunt around the winding of saidrelay.

. HAROLD T. SEELEY.

